Paul A. Farber

Microbiologic factors in endodontology

The role of microorganisms in the cause of endodontic lesions has been intensively investigated. Bacterial components such as endotoxin and other cell wall components are implicated in the development of pulpal and periapical inflammation. Newer anaerobic microbiologic techniques have facilitated accurate and reproducible identification of endodontic pathogens, some of which have been reclassified. This article reviews and correlates newer microbiologic findings with clinical symptoms.

Endodontic microbiology. I. Etiology

The role of bacteria in the etiology of endodontic lesions has been intensively studied. Recent work has elucidated specific mechanisms by which bacterial components such as endotoxin and other cell wall components can contribute to the inflammatory processes. In addition, developments in anaerobic microbiology have facilitated accurate and reproducible identification of endodontic pathogens. This article reviews and correlates clinical and laboratory research bearing on this important topic.

Scanning electron microscopy of cells from periapical lesions

Examination of lymphocytes from peripheral blood with the scanning electron microscope (SEM) has shown differences between B cells and T cells on the basis of their surface architecture. This study was initiated to determine whether the cellular components of periapical lesions could be identified with the use of similar criteria. Cells were dispersed from lesions by aspiration of fragments of tissue through syringe needles of decreasing diameters. The liberated cells were filtered on silver-coated Flotronic membranes and examined under the SEM. Lymphocytes, macrophages, epithelial cells, and mast cells were observed in granulomas and cysts. Most of the lymphocytes had smooth surfaces similar to that of T cells; others had villous projections similar to that of B cells. Epithelial nests were seen in the cyst linings while the cyst fluid was rich in lymphocytes. These findings suggest that SEM examination of periapical lesions can be a useful adjunct in studying cellular composition and possible immunological reactions in these tissues.

Adherence of streptococci to cells infected with herpesvirus

The attachment of streptococci and staphylococci to cells infected with influenza virus has been previously reported and has been correlated with the increased incidence of these bacterial infections during flu epidemics. The present work was initiated to determine whether infection with herpes simplex virus (HSV) might lead to preferential bacterial attachment. HEp-2 cells were grown in monolayer and infected with HSV, Type I or Type II. Twenty-four hours later the cells were incubated with suspensions of various organisms, including Group A and B streptococci, Staphylococcus aureus, Propionibacterium acnes, and Candida albicans. After incubation for one hour, the cells were washed and fixed. Bacterial adherence and virus infection were assessed by scanning electron microscopy (SEM) as well as conventional light and transmission electron microscopy (TEM). Only Group A streptococci adhered to virus-infected cells, both to cells infected with HSV, Type I and those infected with HSV, Type II. SEM and TEM revealed bacteria attaching to cells with budding virus particles. Preincubation of infected cells with anti-HSV serum prevented bacterial adherence. These findings suggest that infection of oral epithelium with HSV might lead to superinfection with Group A streptococci.

The disappearing amalgam: Diagnosis of root fracture

Abstract An unusual case is reported in which apical amalgam seals were found to have been dislodged 5 days after they were placed.

INTERACTION OF VIRUSES WITH LYMPHOID CELLS

Publisher Summary This chapter discusses the interaction of viruses with lymphoid cells. Many tumor viruses, especially the leukemogenic oncornaviruses, are markedly immunosuppressive, especially during the initial stages of the tumorigenic process. It is suggested that immunosuppression associated with tumor virus infection may be a necessary prerequisite for development and appearance of a virus-induced malignancy. Various studies have shown that the murine leukemia viruses can interact with antibody-forming cells and their precursors. Infection with MuLV may also affect T cell immunity and macrophages. Infection of tumor virus susceptible mouse strains with a leukemia virus may result in rapid depression of immune responsiveness to a wide variety of antigens, including both T dependent and independent. Immunosuppression often develops prior to overt symptoms of the disease, and the level of suppression is directly related to virus dose and the time interval between virus injection and challenge immunization. Studies with intact animals have shown that leukemia viruses appear to preferentially affect B lymphocytes that are the precursors of antibody-forming immunocytes.

Changes in Murine Lymphocyte Surface Topography Induced by Friend Virus Infection

Publisher Summary This chapter provides an overview of the changes in murine lymphocyte surface topography induced by a friend virus infection. The infection of susceptible strains of mice with an oncornavirus, such as Friend leukemia virus (FLV), invariably results in marked immunodepression, which generally precedes the overt symptoms of disease, such as splenomegaly and blood cell dyscrasia. The chapter describes a study in which the surface topography of splenocytes in FLV-infected mice was examined by scanning electron microscopy. A correlation was readily made between the changes in the number of cells with distinctive topography and cells staining with fluoresceinated antibody to immunoglobulin or theta antigen. It was found from the study that within a few days after infection, the percentage of cells staining with these anti-FLV serums (reagents) decreased markedly. These results indicate that a marked alteration of cell types occurs in the spleen of FLV-infected mice and these changes correlate with an alteration of cell surface.

Surface Morphology of Leukemia Virus-Infected Lymphoid Cells

The malignant transformation of normal cells by tumor viruses, both in vivo and in vitro, is the subject of much current interest. Infection of mice with Friend Leukemia virus (FLV) produces marked changes to lymphoid cells which results in a generalized immunosuppression (3,10,11). Results of various studies in this and other laboratories indicate that the virus preferentially affects antibody precursor cells rather than antibody forming cells (6,8). Examination of spleen cells from FLV-infected mice with the transmission electron microscope (TEM), has shown the presence of C type particles as well as viruses budding from immature blastlike lymphoid cells (1,9). The present investigation deals with changes in the surface morphology of lymphoid cells which can be detected with the scanning electron microscope (SEM) in mice infected with FLV and correlates these with immunosuppression.